U.S. patent number 7,166,327 [Application Number 10/392,977] was granted by the patent office on 2007-01-23 for method of preparing a conjugated molecular assembly.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Ali Afzali-Ardakani, Cherie Renee Kagan.
United States Patent |
7,166,327 |
Afzali-Ardakani , et
al. |
January 23, 2007 |
Method of preparing a conjugated molecular assembly
Abstract
A method for preparing an extended conjugated molecular assembly
includes applying onto a surface of a substrate a first molecular
compound G1-Molecule1-G2, where G1 includes a first functional
group, G2 includes a second functional group, and Molecule1
includes a conjugated organic group bonded to G1 and G2, and
reacting the first molecular compound with a second molecular
compound G3-Molecule2-G4, where G3 includes a third functional
group. G4 includes a fourth function group, and Molecule 2 includes
a conjugated organic group bonded to G3 and G4, to form on the
substrate an extended conjugated molecule
G1-Molecule1-Molecule2-G4.
Inventors: |
Afzali-Ardakani; Ali (Yorktown
Heights, NY), Kagan; Cherie Renee (Ossining, NY) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
32988010 |
Appl.
No.: |
10/392,977 |
Filed: |
March 21, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20040183069 A1 |
Sep 23, 2004 |
|
Current U.S.
Class: |
427/301;
427/407.1 |
Current CPC
Class: |
B82Y
10/00 (20130101); B05D 1/185 (20130101); B82Y
40/00 (20130101); B82Y 30/00 (20130101); H01L
51/0595 (20130101); H01L 51/0036 (20130101); H01L
51/0068 (20130101); H01L 51/0038 (20130101); B05D
7/52 (20130101); H01L 51/0077 (20130101); H01L
51/0041 (20130101); H01L 51/0035 (20130101); H01L
51/004 (20130101); H01L 51/0512 (20130101) |
Current International
Class: |
B05D
3/10 (20060101) |
Field of
Search: |
;427/301,377,402,407.1,407.2,409,412.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Colvin, V.L. "Semiconductor Nanocrystals Covalently Cound to Metal
Surfaces with Self-Assembled Monolayers" Journal American Chemical
Society 1992, vol. 114, pp. 5221-5230. cited by other .
International Search Report (in International Application
PCT/US2004/008401) dated Apr. 7, 2005. cited by other.
|
Primary Examiner: Fletcher, III; William Phillip
Attorney, Agent or Firm: Tuchman, Esq.; Ido McGinn IP Law
Group PLLC
Claims
What is claimed is:
1. A method for preparing an extended conjugated molecular
assembly, said method comprising: applying onto a surface of a
substrate a first molecular compound G1-Molecule1-G2, where G1
comprises a first functional group, G2 comprises a second
functional group, and Molecule1 comprises a conjugated organic
group bonded to G1 and G2 and reacting said first molecular
compound with a second molecular compound G3-Molecule2-G4, where G3
comprises a third functional group, G4 comprises a fourth function
group, and Molecule 2 comprises a conjugated organic group bonded
to G3 and G4, to form on said substrate an extended conjugated
molecule G1-Molecule1-Molecule2-G4, wherein first functional group
G1 interacts with said substrate, and wherein said second
functional group G2 and said third functional group G3 are replaced
by a covalent bond between carbon atoms in said first and second
molecular compounds.
2. A method for preparing an extended conjugated molecular
assembly, said method comprising: applying onto a surface of a
substrate a first molecular compound G1-Molecule1, where G1
comprises a first functional group, and Molecule1 comprises a
functional organic group bonded to G1; treating an end of said
first molecular compound G1 -Molecule1 to form on said substrate a
second molecular compound G1-Molecule 1-G2, where G2 comprises a
second functional group; and reacting said second molecular
compound with a third molecular compound G3-Molecule2 to form on
said substrate an extended conjugated molecule G1-Molecule
1-Molecule2.
3. The method according to claim 2, further comprising: preparing
an end of one of said second molecular compound and said extended
conjugated molecule with a functional group G4.
4. A method for preparing an extended conjugated molecular
assembly, said method comprising: applying onto a surface of a
substrate a first molecular compound G1-Molecule1-G2, where G1
comprises a first functional group, G2 comprises a second
functional group, and Molecule1 comprises a conjugated organic
bonded to G1 and G2; and reacting said first molecular compound
with a second molecular compound G3-Molecule2-G4, where G3
comprises a third functional group, G4 comprises a fourth function
group, and Molecule 2 comprises a conjugated organic group bonded
to G3 and G4, to form on said substrate an extended conjugated
molecule G1 -Molecule1-Molecule2-G4, wherein the first molecular
compound comprises a molecule represented by the following chemical
formula ##STR00019##
5. A method for preparing an extended conjugated molecular
assembly, said method comprising: applying onto a surface of a
substrate a first molecular compound G1-Molecule1-G2, where G1
comprises a first functional group, G2 comprises a second
functional group, and Molecule1 comprises a conjugated organic
group bonded to G1 and G2; and reacting said first molecular
compound with a second molecular compound G3-Molecule2-G4, where G3
comprises a third functional group, G4 comprises a fourth function
group, and Molecule 2 comprises a conjugated organic group bonded
to G3 and G4, to form on said substrate an extended conjugated
molecule G1-Molecule1-Molecule2-G4, wherein the first molecular
compound comprises a molecule represented by the following chemical
formula ##STR00020##
6. A method for preparing an extended conjugated molecular
assembly, said method comprising: applying onto a surface of a
substrate a first molecular compound G1-Molecule1-G2, where G1
comprises a first functional group, G2 comprises a second
functional group, and Molecule1 comprises a conjugated organic
group bonded to G1 and G2; and reacting said first molecular
compound with a second molecular compound G3-Molecule2-G4, where G3
comprises a third functional group, G4 comprises a fourth function
group, and Molecule2 comprises a conjugated organic group bonded to
G3 and G4, to form on said substrate an extended conjugated
molecule G1-Molecule1-Molecule2-G4, wherein said first functional
group G1 is selected from the group consisting of: phosphine oxide,
phosphonic acid, hydroxamic acid, phosphite, phosphate,
phosphazine, azide, hydrazine, sulfonic acid, sulfide, disulfide,
aldehyde, ketone, silane, germane, arsine, nitrile, isocyanide,
isocyanate, thiocyanate, isothiocyanate, amide, alcohol, selenol,
nitro, boronic acid, ether, thioether, carbamate, thiocarbamate,
dithiocarbamate, dithiocarboxylate, xanthate, thioxanthate,
alkylthiophosphate, dialkyldithiophosphate and any combination
thereof.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This Application is related to U.S. patent application Ser. No.
10/392,983 filed on Mar. 21, 2003, entitled "ELECTRONIC DEVICE
INCLUDING A SELF-ASSEMBLED MONOLAYER, AND A METHOD OF FABRICATING
THE SAME", assigned to International Business Machines Corporation,
and incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a conjugated molecular assembly, a
method of fabricating the assembly, and a device including the
assembly and, in particular, a conjugated molecular assembly having
an extended conjugated segment.
2. Description of the Related Art
During the past three decades, renewed interest and considerable
progress has been made in the synthesis and chemical and physical
understanding of conjugated molecules and macromolecules. The
attention is largely driven by applications of conjugated molecular
assemblies in optical, optoelectronic, electronic, and sensor
applications.
Most conjugated molecular assemblies include small molecules or
short-chain oligomers, less than 8 monomeric units long. These
small molecules may be found in nature, readily prepared by common
organic synthetic techniques, and manipulated in organic
solvents.
The nature of the .pi.-bonding that gives rise to conjugation and
the interesting physical properties is also the source of molecular
rigidity and insolubility. As the size of conjugated molecules
increases, they become increasingly less soluble. For example, in
the homologous oligothiophene series quaterthiophene (4 thiophene
monomers) is soluble, but sexithiophene (6 thiophene monomers) is
not soluble. The insolubility of these assemblies can in some cases
be overcome by chemically functionalizing the end or sides of
conjugated molecules, but this also may change the desirable
physical properties of the molecules and their assemblies.
Very long molecules (e.g., greater than 20 monomers long) are
typically classified as polymers. Polymers are polydisperse and
characterized by their average molecular weight. Polymer chains
consist of a distribution of shorter, rigid molecular segments.
This gives rise, especially when functionalized, to solubility not
found in shorter molecules and oligomers, but also to a
distribution in physical properties and a lack of order in
polymeric thin films.
Recently, sequential synthetic routes to prepare well-defined
molecules and macromolecules has been demonstrated [J. M. Tour,
"Conjugated Macromolecules of Precise Length and Constitution.
Organic Synthesis for the Construction of Nanoarchitectures," Chem.
Rev. 96, 537 (1996), P. R. L. Malenfant, J. M. J. Frechet, "The
first solid-phase synthesis of oligothiophenes," Chem. Comm., 23,
2657 (1998).) by solution-phase chemical techniques and on resins
(solid supports). While some assemblies have been synthesized,
these techniques do not enable assembly onto surfaces.
Chemical functionalization of short molecules with head groups that
enable the binding to and the self-assembly of molecules onto
surfaces has received enormous attention. Once assembled onto a
surface these molecular layers are known as self-assembled
monolayers (SAMs). These molecules are typically synthesized and
then allowed to self-assemble from common solvents onto surfaces.
Self-assembled monolayers have received tremendous attention as
etch barriers, surface layers to alter surface chemistry, and
resist layers.
Conjugated SAMs have received particular interest as active layers
in molecular electronic and photonic devices and have more recently
been discussed as the active layers in molecular sensors. The SAMs
investigated to date are typically short conjugated molecular
segments as the longer molecules, which may be interesting for
devices, are no longer soluble and therefore have not been
investigated. Molecular electronic and memory devices are based on
intramolecular charge transport and building the desired
functionality, such as switching, within the molecule. Molecular
sensors may also be based on changes in intramolecular charge
transport arising from the detection of an analyte by a receptor
that is a part of the molecule. A molecular scale transistor is a
necessary component for logic applications and has often been
referred to as the holy grail of molecular electronics.
To build a molecular scale transistor is no small feat. The channel
length of a molecular transistor is defined by the length of the
molecule. Similarly, the molecular switching medium in a memory
cell or the functionalized molecule in a molecular sensor defines
the interelectrode distance. In order to attain a suitable
"off-state" of a molecular device in both transistors and memory
cells and a measurable change in resistance in a sensor, the
tunneling current between electrodes (source and drain electrodes
in a transistor) must be suppressed. This places a lower limit on
the channel length or cell height in transistors and memory cells,
respectively, and therefore the length of the molecule at about 2.5
nm 3.0 nm [C. R. Kagan, A. Afzali, R. Martel, L. M. Gignac, P. M.
Solomon, A. G. Schrott, B. Ek, "Evaluations and Considerations for
Self-Assembled Monolayer Field-Effect Transistors," Nano Letters,
3, 119 (2003)]. The lower limit on the channel length and the
length of the molecule is also constrained in a molecular
field-effect transistor by electrostatics and the requirement to
introduce a sufficient gate field to modulate the conductance of
the molecular channel. This may also be true in a chemical
field-effect transistor for sensing. The self-assembled conjugated
molecules that have been investigated are typically shorter than
2.5 nm 3.0 nm.
The desired functionality of a molecular device may necessitate the
incorporation of different molecular segments. The long-term vision
of building the entire functionality of a molecular device within
the molecule may require the introduction of different molecular
species with different chemical and physical function. To date,
only very simple and short conjugated self-assembled molecules have
been investigated and therefore have not incorporated some of the
desired molecular functionality.
Layer-by-layer assembly techniques have been used to prepare longer
length scale molecular assemblies on surfaces. One of the most
developed assemblies grown layer-by-layer is the layered metal
phosphates and phosphonates. The films include multivalent metal
ions, e.g. Zr.sup.4+, and organic molecules terminated with an
acidic functionality, such as a phosphonic acid [e.g., see Cao,
Hong, Mallouk, "Layered Metal Phosphates and Phosphonates: From
Crystals to Monolayers" Acc. Chem. Res., 25, 420 (1992)].
Katz and co-workers have used this method to align hyperpolarizable
molecules into polar multilayer films that show second-order
nonlinear optical effects (e.g., see U.S. Pat. Nos. 5,217,792 and
5,326,626). A similar approach has also been extended to other
materials such as polymers, natural proteins, colloids, and
inorganic clusters [e.g., see Decher, "Fuzzy Nanoassemblies: Toward
Layered Polymer Multicomposites," Science 277,1232 (1997)]. This
same technique has also been applied to the production of other
multilayers including Co-diisocyanide, dithiols with Cu, and
pyrazines with Ru [e.g., see Page, Langmuir, "Coordinate Covalent
Cobalt-Diisocyanide Multilayer Thin Films Grown One Molecular Layer
at a Time" 16, 1172, (2000)].
Among the existing examples, the driving force for the film
progression is mainly the electrostatic interactions between
polycations and polyanions. Few examples involve other types of
interactions, such as hydrogen bond, covalent, or mixed
covalent-ionic. Recently the inventors demonstrated the use of
strong covalent interactions, rather than ionic interactions,
between metals and ligands in a novel strategy to assemble nearly
perfectly packed multilayers of metal-metal bonded supramolecules
and utilized this approach in molecular devices (YOR920010784US1,
YOR920020094US1, C. Lin, C. R. Kagan, "Layer-by-Layer Growth of
Metal-Metal Bonded Supramolecular Thin Films and Its Use in the
Fabrication of Lateral Nanoscale Devices," J. Am. Chem. Soc., 125,
336 (2003)). While there are a few examples of layer-by-layer
assembly using covalent interactions, none of the examples allow
for carbon-carbon bond formation.
To harness the optical, optoelectronic, electronic, and sensor
properties of conjugated molecular assemblies in solid-state
applications and devices, development of new methods for
incorporating molecules with longer molecular lengths and with a
wide range of functionality are needed. Layer-by-layer assembly
methods, while attractive for the formation of extended molecular
structures, have not been demonstrated for the formation of
carbon-carbon bonds necessary to form the extended conjugated
molecular assemblies interesting for applications.
SUMMARY OF THE INVENTION
In view of the foregoing and other problems, disadvantages, and
drawbacks of the conventional assemblies and methods, it is a
purpose of the present invention to provide a conjugated molecular
assembly (and method of fabricating the assembly) which includes
molecules with long molecular lengths (e.g., extended conjugated
molecules) and allows for a wide range of functionality.
In a first aspect, the present invention includes a conjugated
molecular assembly which includes a substrate, and an extended
conjugated molecule attached to the substrate. The extended
conjugated molecule includes a first conjugated molecule having a
first functional group for attaching to the substrate, and a second
conjugated molecule which is covalently linked to the first
conjugated molecule.
The present invention also includes an inventive method of
fabricating a conjugated molecular assembly. The inventive method
includes applying a first conjugated molecule having a first
functional group on a substrate, and covalently linking a second
conjugated molecule to the first conjugated molecule to form an
extended conjugated molecule.
Specifically, the inventive method may involve the stepwise
construction of covalently linked assemblies of conjugated
molecular assemblies. More particularly, the present invention
provides a means for carbon-carbon bond formation of extended
conjugated molecular assemblies and for the introduction of
different molecular species to impart functionality into molecular
assemblies.
In addition, the present invention provides an inventive molecular
electronic device. The device may include source and drain regions
(e.g., source and drain electrodes), a molecular medium extending
therebetween, and an electrically insulating layer between the
source region, the drain region and the molecular medium (this is
for transistors and sensors). The device may include two electrodes
interposed with a molecular medium extending therebetween (this is
for memory and sensors). The inventive molecular device may be used
for memory or logic or sensor devices. The molecular medium in the
molecular device according to the present invention includes an
extended conjugated molecular assembly which may be prepared by
stepwise construction.
More specifically, the present invention provides a method for
constructing assemblies of conjugated molecular assemblies of
controlled length and molecular constitution on surfaces.
For example, the inventive method may include applying onto a
surface of a substrate a first molecular compound represented by
the formula G1-Molecule1-G2, to produce a primer layer of the first
molecular compound on the substrate, where G1 includes a functional
group for interacting with the surface of the substrate; G2
includes a functional group for reacting with a subsequently added
molecule, and Molecule.sub.A includes a conjugated organic group
bonded to G1 and G2, reacting the primer layer with a second
molecular compound to produce a covalently linked molecular layer
on the primer layer, the second molecular compound being
represented by the formula G3-Molecule2-G4, and is capable of
reacting with another functionalized molecule, to produce a
sequentially grown assembly having covalently linked molecular
assemblies bound to a self-assembled monolayer. The method may also
include sequentially repeating reacting a second (in the sequence
this would be a third molecular compound) molecular compound with
G4 at least once to further extend the molecular assembly.
In another example, the inventive method includes applying onto a
surface of a substrate a first molecular compound represented by
the formula G1-Molecule1 to produce a primer layer of the first
molecular compound on the substrate, where G1 includes a functional
group capable of interacting with the surface of the substrate and
Molecule1 includes a functional organic group bonded to G1,
treating the end of the molecular layer G1-Molecule1 to form a
compound G1-Molecule1-G2, where G2 includes a functional group for
reacting with a subsequently added molecule, reacting the primer
with a molecular assembly to produce a covalently linked molecular
layer on the primer layer; the molecular layer being selected from
the group consisting of compounds represented by the following
formulas G3-Molecule2, and preparing an end of the second molecular
compound with a reacting functional group as G4, where G4 includes
the same or different functional group as G2, and is capable of
reacting with another functionalized molecule, to produce a
sequentially grown assembly having covalently linked molecules
bound to a self-assembled monolayer. Further, the method may
include sequentially repeating the treating the end of the
molecular layer G1-Molecule1 and the preparing an end of the second
molecular compound at least once to further extend the molecular
assembly.
Alternatively, other methods of fabricating the inventive assembly
may combine or modify portions of the above-described methods to
couple molecules. These other methods may include, for example,
electrostatic, hydrogen bonding, ionic, covalent, and mixed
ionic-covalent interactions, which are known in the art, or by
electrochemical coupling.
More particularly, the present invention provides a method for
preparing an assembly having an extended conjugated assembly. For
example, one example (e.g., Route A in FIG. 3) of the method
includes applying onto a surface of a substrate a first molecular
compound represented by the formula G1-Molecule1-G2 to produce a
primer layer of the first linker compound; where G1 is selected
from the group consisting of silane, phosphonic acid, hydroxamic
acid, isocyanide, and thiol, G2 is selected from the group
consisting of halogens, diazo, ethynyl, trialkyl tin, boronic acid,
zinc halide, and hydrogen, Molecule1 is selected from the following
groups represented by chemical formulas 1 11:
##STR00001## ##STR00002## or any combination thereof. In addition,
the method includes reacting the primer with a molecular assembly
to produce a covalently linked molecular layer on the primer layer;
the molecular layer being selected from the group consisting of
compounds represented by the following formula G3-Molecule2-G4,
where Molecule2 may be the same or a different molecular species as
Molecule1 and selected from the groups having a chemical formula 1
11 described above, or any combination thereof, and where G4 may be
the same as or different functional groups than G2, but is capable
of reacting with another functionalized molecule. The method may
also include sequentially repeating steps the step of reacting with
another molecule at least once to produce the sequentially grown
assembly having covalently linked molecular assemblies bound to the
self-assembled monolayers.
Alternatively, the inventive method may include the steps of Route
B in FIG. 4 which includes applying onto a surface of a substrate a
first molecular compound represent by the formula G1-Molecule1, to
produce a primer layer of the first linker compound; where G1 is
selected from the group consisting of: silane, phosphonic acid,
hydroxamic acid, isocyanide, and thiol; Molecule1 is selected from
the groups having chemical formulas 1 11, as described above, or
any combination thereof. In addition, the method includes treating
the end of the molecular layer G1-Molecule1 to prepare
G1-Molecule1-G2, where G2 is selected from the group consisting of:
halogens, trialkyl tin, diazo, ethynyl, boronic acid, zinc halide,
hydrogen, and vinyl, and reacting the primer with a molecular
assembly to produce a covalently linked molecular layer on the
primer layer; the molecular layer being selected from the group
consisting of compounds represented by the following formula
G3-Molecule2, where Molecule2 may be the same or a different
molecular species as Molecule1 and selected from the groups having
the chemical formulas 1 11, as described above, or any combination
thereof., and preparing the end of the added molecular layer with a
reacting functional group as G4, wherein G4 may be the same as or
different functional groups than G2, but is capable of reacting
with another functionalized Molecule. The method may also include
sequentially repeating steps of reacting the molecule and preparing
the end group at least once to produce the sequentially grown
assembly having covalently linked molecular assemblies bound to the
self-assembled monolayers.
The present invention further provides for an assembly having
functionality introduced by constructing assemblies using different
molecular species. Such assemblies can be prepared by the method
according to the present invention.
The present invention also includes a molecular device which
includes an extended conjugated molecular assembly according to the
present invention. For example, the device may include a substrate
(e.g., Au, Pd, indium tin oxide, ZrO2, SiO.sub.2), a source region
and drain region which are adjacent to the substrate, and a
molecular medium including an extended conjugated molecule formed
between the source region and drain region.
For example, the inventive molecular device may include a source
region and a drain region, a molecular medium extending between the
source region and the drain region, and an electrically insulating
layer between the source region, the drain region and the molecular
medium. The device may be modified, for instance, to include a
floating electrode formed on the insulating layer between two
portions of the molecular medium.
In another example, the molecular device includes a source region
and a drain region, a molecular medium extending between the source
region and the drain region, the molecular medium including an
assembly having an extended conjugated molecular assembly (e.g.,
prepared by stepwise construction), a gate region disposed in
spaced adjacency to the molecular medium, and an electrically
insulating layer between the gate region and the source region, the
drain region and the molecular medium. The device may be modified,
for instance to include a floating electrode formed on the
insulating layer between two portions of the molecular medium
In another example, the inventive molecular device includes a
source region and a drain region, a molecular medium extending
between the source region and the drain region
In another example, the molecular device includes a source region
and a drain region, a molecular medium extending between the source
region and the drain region (e.g., either vertically or laterally),
the molecular medium including an assembly having an extended
conjugated molecular assembly (e.g., prepared by stepwise
construction), and a gate region disposed in spaced adjacency to
the molecular medium, and an electrically insulating layer between
the gate region and the source region, the drain region and the
molecular medium
With its unique and novel features, the present invention includes
a conjugated molecular assembly (and method of fabricating the
assembly) which includes molecules with long molecular lengths
(e.g., extended conjugated molecules) and allows for a wide range
of functionality. The present invention also provides an improved
molecular device having improved electrical or sensor
properties.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, aspects and advantages will be
better understood from the following detailed description of
preferred embodiments of the invention with reference to the
drawings, in which:
FIG. 1 illustrates a conjugated molecular assembly 100 according to
the present invention;
FIG. 2 illustrates a method 200 of fabricating a conjugated
molecular assembly according to the present invention;
FIGS. 3 6 illustrate exemplary methods 300, 400, 500, 600 of
fabricating a conjugated molecular assembly according to the
present invention;
FIGS. 7A 7B illustrate examples of a donor-acceptor assembly 700,
and a molecular assembly with redox-active species 750,
respectively, which may be fabricated according to the present
invention;
FIG. 8 illustrates a molecular device 800 (e.g., a 2-terminal
lateral device structure) including an extended conjugated
molecular layer as the active switching medium between two
electrodes, according to the present invention;
FIG. 9 illustrates a molecular device 900 (e.g., a 2-terminal
lateral device structure) including an extended conjugated
molecular layer as the active switching medium with a floating
electrode between two electrodes, according to the present
invention;
FIG. 10 illustrates a molecular device 1000 (e.g., a 3-terminal
lateral device structure) including an extended conjugated
molecular layer as the active switching medium between source and
drain electrodes and separated from the gate electrode by an
insulator, according to the present invention;
FIG. 11 illustrates a molecular device 1100 (e.g., a 3-terminal
lateral device structure) including an extended conjugated
molecular layer as the active switching medium and a floating
electrode between source and drain electrodes and separated from
the gate electrode by an insulator, according to the present
invention;
FIG. 12 illustrates a molecular device 1200 (e.g., a 2-terminal
vertical device structure) including an extended conjugated
molecular layer as the active switching medium between two
electrodes, according to the present invention;
FIG. 13 illustrates a molecular device 1300 (e.g., a 3-terminal
vertical device structure) including an extended conjugated
molecular layer as the active switching medium between source and
drain electrodes and separated from the gate electrode by an
insulator, according to the present invention; and
FIGS. 14A 14B illustrate a molecular sensor 1400, 1450 including an
extended conjugated system functionalized with receptors as the
active sensing medium between two electrodes (e.g., source and
drain electrodes), according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
Referring now to the drawings, FIG. 1 illustrates a conjugated
molecular assembly 100 according to the present invention. As shown
in FIG. 1, the inventive molecular assembly 100 includes a
substrate 110, and an extended conjugated molecule 120 which
includes a first conjugated molecule 130 which is formed on the
substrate 110, and a second conjugated molecule 140 which is
covalently linked to the self-assembled monolayer 130. Further, a
functional group 150 (e.g., a head functional group) may be used to
attach (e.g., bond or adsorb) the first conjugated molecule to the
substrate 110.
The present invention also includes an inventive method of
fabricating a conjugated molecular assembly. As shown in FIG. 2,
the inventive method 200 includes applying (210) a first conjugated
molecule (e.g., having a first functional group) on a substrate,
and covalently linking (220) a second conjugated molecule to the
first conjugated molecule to form an extended conjugated
molecule.
The inventive method may include the stepwise construction of
conjugated molecules on a self-assembled monolayer to form a
covalently linked assembly (e.g., a conjugated molecular assembly).
More particularly, the assembly may be connected through
carbon-carbon covalent bonds. Such a structure may have many
applications in solid-state molecular electronic, optoelectronic,
optical, and sensor applications.
More specifically, the inventive assembly 100 may be prepared by
repeated sequential construction of small molecules to produce
molecules of controlled length and chemical constitution. The
inventive method 200 of fabricating the assembly may be considered
self-assembling, stepwise, and tunable.
Upon application onto a substrate, the conjugated molecule of the
self assembled monolayer 130 is adsorbed (or chemically bonded) on
the substrate. Thereafter, at least one additional conjugated
molecule (e.g., a plurality of conjugated molecules) may be added
(e.g., sequentially added) end-to-end so as to form an extended
segment. Thus, a layer-by-layer growth of the assemblies can be
achieved by this "stepwise" approach. Further, the multi-layered
assemblies can be grown layer-by-layer to the desired length.
In one exemplary embodiment, the inventive method may include:
(1) applying onto a surface of a substrate a first molecular
compound represented by the formula; G1-Molecule1-G2 to produce a
primer layer of the first molecular compound on the substrate,
where G1 includes a functional group capable of interacting with
the surface of the substrate, G2 includes a functional group
capable of reacting with an added molecule, and Molecule1 includes
an organic group (e.g., conjugated molecule) bonded to G1 and
G2;
the conjugated molecule being selected from the group consisting of
compounds represented by the following formulas 1 11:
##STR00003## ##STR00004## and a combination thereof; where each of
R, S, T, U, V, W, X, Y, and Z is a substituent (e.g., a hydrogen,
an organic group or non-organic group), and where d, e, f, g, h, i,
j, k, m, n, include integers from 1 to 10;
(2) applying onto Molecule1 a second molecular compound represented
by the formula: G3-Molecule2-G4 to produce an extended conjugated
molecular assembly, where G3 and G4 are the same or different
functional groups capable of reacting with Molecule1-G2; and
Molecule2 is an organic group (e.g., a conjugated molecule) bonded
to G3 and G4. Further, Molecule2 may include an organic group
selected from the above described groups having chemical formulas 1
11, and may be the same as Molecule 1 or different than
Molecule1.
Further, (2) above may be sequentially repeated to produce the
sequentially grown (e.g., layer by layer) assembly having
covalently linked molecular assemblies bound to the self-assembled
monolayers.
The length, functionality, direction of molecule vector, and other
physical and chemical properties of each layer can be tuned by
varying the molecules added. This feature may be used to tune the
physical properties of the molecular assembly (for example
absorption, fluorescene, polarizability, electronegativity, ability
to hydrogen bond, coordination to metals), and also to prepare
donor-acceptor compounds, redox-active assemblies, and assemblies
functionalized with receptors sensitive to chemical or biological
agents.
Further, these steps can be combined with other coupling reactions
known in the art. Preferably, the conjugated molecular assembly 100
(e.g., the assembly) has from 1 to 60 conjugated molecular
monomers.
Further, the inventive assembly 100 (e.g., assembly) may be
deposited from a liquid solution and therefore, the assembly 100
may be deposited on substrates having a diverse topography and
configuration.
Referring again to the Figures, FIG. 3 illustrates an example
(e.g., Route A) of the inventive method. Specifically, FIG. 3
illustrates a stepwise construction method which may be used
according to the present invention to fabricate extended conjugated
molecular compounds on a substrate. (In FIG. 3, the symbol
represents a molecule which may be reacted with another molecule to
form carbon-carbon bonds therebetween).
As shown in FIG. 3, the inventive method 300 may include applying
(310) a first compound G1-Molecule1-G2 to a substrate surface,
applying (320) a second compound G3-Molecule2-G4 to the first
compound to form on the substrate, an extended conjugated molecule
G1-Molecule1-Molecule2-G4 Note that in this case, groups G2 and G3
may be selected to interact (e.g., combine) so as to be replaced
with a bond between Molecule1 and Molecule2. The method 300 may
also include again applying (330) a third compound G5-Molecule3-G6
(i.e., repeating step 320), in order to further extend the
conjugated molecule.
FIG. 4 illustrates another example (e.g., Route B) of the inventive
method. Specifically, FIG. 4 illustrates another stepwise
construction method used according to the present invention to
fabricate extended conjugated molecular compounds on a
substrate.
As shown in FIG. 4, the inventive method 400 may include applying
(410) a first compound G1-Molecule1 to a substrate surface,
applying (420) a functional group G2 (e.g., a tail end functional
group) onto Molecule1, and applying (430) a compound Molecule 2 so
that Molecule 2 bonds (e.g., forms a carbon-carbon covalent bond)
with Molecule1, and replaces functional group G2.
The method 400 may also include repeating (440) earlier steps
(e.g., steps (420) and (430)) to further extend the extended
conjugated molecule.
In addition, it should be noted that aspects of these inventive
methods 300, 400 may be combined and modified to fabricate the
inventive assembly. For example, steps (410) and (420) of method
400 may be performed to generate the compound G1-Molecule1-G2 on a
substrate surface, Then, step (320) of method 300 may be performed
to generate the compound G1-Molecule1-Molecule2-G4 on the substrate
surface, and so on.
Referring again to FIG. 1, with respect to the substrate 110, any
suitable material can be used. Suitable substrates include, for
example, a metal, a metal oxide, a semiconductor, a metal alloy, a
semiconductor alloy, a polymer, an organic solid, and a combination
thereof. The form of the substrates can be a planar solid or a
non-planar solid such as a stepped or curved surface.
The following preferred substrates have been demonstrated: Au, Pd,
ITO, ZrO.sub.2, and SiO.sub.2.
The G1-Molecule1-G2 compound is a molecular species that can form a
self-assembled monolayer. Suitable compounds include organic
molecular species having a functional group G1 capable of
interaction with the surface of the substrate forming a coated
surface.
The functional groups G1 that can be included in these compounds
for interacting with or binding to a particular substrate surface
with chemical specificity. For example, the G1 functional group may
include one or more of the same or different functional groups,
such as phosphine oxide, phosphonic acid, hydroxamic acid,
phosphite, phosphate, phosphazine, azide, hydrazine, sulfonic acid,
sulfide, disulfide, aldehyde, ketone, silane, germane, arsine,
nitrile, isocyanide, isocyanate, thiocyanate, isothiocyanate,
amide, alcohol, selenol, nitro, boronic acid, ether, thioether,
carbamate, thiocarbamate, dithiocarbamate, dithiocarboxylate,
xanthate, thioxanthate, alkylthiophosphate, dialkyldithiophosphate
or any combination thereof.
Functional group G2 is capable of reacting with the next layer of
molecules (e.g., a functional group on the next layer).
Specifically, this group that can be included in a molecule for
interacting or reacting with a particular conjugated molecule with
chemical specificity, and may include one or more of the same or
different functional groups. Thus, G2 in the first linker compound
can independently include a halogen or a compound having the
chemical formula, --SnR.sub.3 (where R is an alkyl group),
--N.ident.N, --C.ident.CH, --CH.dbd.CH.sub.2, --ZnX (where X is a
halogen), H,
##STR00005## (where R can independently be a hydrogen or an alkyl
group).
Further, the functional groups used to facilitate the linkage
between molecules (e.g., G2, G3, and G4) may be selected from the
same set of groups. However, they must be selected to facilitate
the formation of the carbon-carbon bond. Thus, for example, in the
method 300 discussed above, although the second and third
functional groups, G2 and G3, may be selected from the same set of
groups, they must be different (e.g., G2 may be a halogen, and G3
may be a --SnR.sub.3 group, or vice versa) in order for Molecule1
and Molecule2 to be linked.
For example, compounds having the following chemical formulas 12 13
have been demonstrated to be suitable G1-Molecule1 compounds:
##STR00006## on oxides surfaces, and
##STR00007## on Au and Pd surfaces.
The compounds having the above described chemical formulas 1 11
having a functional group G2 (e.g., X=G2) have been demonstrated to
be suitable for reacting with other molecules, where R, S, T, U, V,
W, X, Y, and Z are substituents (e.g., a hydrogen, or an organic or
inorganic substituent), and where d, e, f, g, h, i, j, k, m, n,
include integers from 1 to 10. Further, any combination of the
groups having chemical formulas 1 11 would be suitable for reacting
with other molecules.
FIG. 5 illustrates a more specific exemplary embodiment of the
inventive method of fabricating a conjugated molecular assembly.
Specifically, FIG. 5 illustrates an example of a method of
fabricating a multilayer assembly on substrates, such as quartz,
indium-tin-oxide (ITO), and silicon wafers that have a native or
thermally grown silicon dioxide surface. As shown in FIG. 5, the
inventive method 500 includes the following:
(1) applying (510) onto a surface of an oxide substrate a first
molecular compound represented by the formula 12:
##STR00008## where the head end group (e.g., G1) is the phosphonic
acid functional group;
(2) brominating (520) the molecule with n-bromosuccinimide (NBS) to
form on the substrate, the compound having the following chemical
formula 14:
##STR00009##
(3) reacting (530) the tail end group (e.g., --Br) with the
compound having the following chemical formula 15:
##STR00010## in the presence of a Pd catalyst to produce on the
substrate, the compound having the following chemical formula
16:
##STR00011##
In addition, steps (520) and (530) above may be repeated at least
once to further extend the conjugated molecular assembly.
FIG. 6 illustrates more specific exemplary embodiment of the
inventive method of fabricating a conjugated molecular assembly.
Specifically, FIG. 6 illustrates an example of a method of
fabricating a multilayer assembly on substrates, such as gold and
palladium. As shown in FIG. 6, the inventive method 600 includes
the following:
(1) applying (610) onto a surface of a substrate a first molecular
compound represented by the chemical formula 13:
##STR00012## where G1 includes the head group isocyanide;
(2) electrochemically coupling (620) to the compound (i.e.,
chemical formula 13) to the compound having the chemical formula
17:
##STR00013## to construct on the substrate a compound having the
following chemical formula 18:
##STR00014##
(3) reacting (630) this compound (chemical formula 18) with another
molecule having the following chemical formula 19,
##STR00015## in the presence of a Pd catalyst to construct the
compound having the following chemical formula 20:
##STR00016##
(4) electrochemically coupling (640) to this compound (chemical
formula 20) to the molecule having the following chemical formula
13:
##STR00017## to construct on the substrate, the extended conjugated
molecule having the following chemical formula 21:
##STR00018##
The above reaction sequences show the two general routes used to
form extended conjugated assemblies using carbon-carbon bond
formation. These two methods depend on the synthetic reactions used
to link different molecular species. The deposition begins with the
chemical modification of the substrates. The reagents used to carry
out this modification are chosen so that they bear two functional
groups at both ends, namely head groups and tail groups.
The head groups (e.g., G1) are chosen to chemically bind to the
particular substrate surfaces. For example, the head group can be a
silane, phosphonic acid, hydroxamic acid, or carboxylic acid to
functionalize oxide surfaces, or a thiol/thiolate, nitrile,
phosphine, sulfide, or selenide to functionalize metal or
semiconductor surfaces. The tail groups will template the growth of
the conjugated molecular assemblies.
In the first step, the substrates used for film growth can be
various kinds of metals, insulators, and semiconductors such as
glass, quartz, aluminum, gold, palladium, platinum, gold/palladium
alloy, silicon, thermally grown silicon dioxide on silicon, and
indium-tin-oxide coated glass. Since the films are deposited from
liquid solutions, they may be deposited on substrates having
diverse topography and configuration. The form of the substrates
can be a planar solid or a non-planar solid such as a stepped or
curved surface.
The second step of thin film deposition is to treat the modified
substrate with an appropriate compound and reagents containing at
least one conjugated molecule from solution. The conjugated
molecules will react with the primer layer.
The next step is to repeat the above step to add additional layers,
but the conjugated molecules are not required to be the same. This
provides a versatile means of assembling multilayer
heterostructures from various conjugated molecular building blocks,
with essentially any desired sequence of layers.
The present invention provides a means to form a versatile range of
heterostructures by coupling different molecules to provide
functionality. This includes donor-acceptor assemblies such as the
assembling multilayers 700 which are illustrated, for example, in
FIG. 7A. For example, as shown in FIG. 7A, the assemblies may
include molecule1 which includes four thiophene monomers and a
cyanide group attached to the substrate, and a molecule2 which
includes 4 thiophene-s-oxide monomers.
In addition, the molecular assemblies may include redox-active
species such as the assembly 750 illustrated in FIG. 7B. For
example, as shown in FIG. 7B, the assemblies may include molecule 1
which includes 4 thiophene monomers and a cyanide group attached to
the substrate, and a molecule2 which includes a porphyrin
group.
In sum, the present invention makes use of a molecular medium,
which includes an extended conjugated molecule. This molecule may
be prepared, for example, by stepwise construction as the active
switching medium in two- and three-terminal electronic and sensor
devices.
Further, the inventive conjugated molecular assembly has a
well-defined length and molecular constitution. The properties of
the inventive molecular assembly may be tuned by the introduction
of different molecular species. As a result, these materials offer
rich electrochemistry and electronic properties for electronic
device applications and receptor sites for sensor device
applications, while being simple and easy to fabricate at room
temperature by inexpensive methods, such as low-cost deposition
from solution.
Referring again to the drawings, FIG. 8 illustrates a molecular
device 800 according to the present invention. Specifically, FIG. 8
illustrates a cross-sectional view of a two-terminal lateral
electronic device 800. This device 800 includes an active switching
medium layer 4 (between electrodes 6 and 8) fabricated on substrate
18, which serves as the active switching medium between electrodes
6 and 8. The active layer 4 (e.g., in combination with the
substrate 18 or one or both of the electrodes 6 and 8, (e.g., where
the assembly is assembled on the sidewall)) includes a conjugated
molecular assembly 100 according to the present invention.
FIG. 9 shows a cross-sectional view of a two-terminal lateral
device 900 according to the present invention. The device 900
includes a floating electrode 30. The device 900 also includes an
active switching medium layer (between electrodes 24 and 26)
fabricated on substrate 28, which has 2 portions 22A, 22B which are
separated by the floating electrode 30, and serves as the active
switching medium between electrodes 24 and 26. Further, the layer
portions 22A, 22B (e.g., in combination with any of the electrodes
24, 26, and 30 (in this case it may be harder to selectively
deposit material on the sides if its grown off the substrate, but
it may be grown off the sidewalls)) includes a conjugated molecular
assembly 100 according to the present invention.
FIG. 10 shows a cross-sectional view of a three-terminal lateral
electronic device 1000 in the configuration of a transistor. The
device 1000 includes a conjugated molecular assembly layer 42 which
(e.g., in combination with insulator 48 or one or both of the
electrodes 44 and 46) includes the conjugated molecular assembly
100 according to the present invention.
Layer 42 serves as the channel between source and drain electrodes
46 and 44. The conductance of the conjugated molecular assembly may
be modulated across an electrically insulating layer 48, such as a
thin SiO.sub.2 film, by a gate electrode 50, which may be a
degeneratively doped silicon layer, all of which are fabricated on
substrate 52.
FIG. 11 shows a cross-sectional view of a three-terminal lateral
electronic device 1100 in the configuration of a transistor with a
floating electrode 74. Layer portions 62A, 62B are portions of a
conjugated molecular assembly layer which are separated by the
floating electrode 74 and include (e.g. in combination with any of
the electrodes 64, 66, and 74) the conjugated molecular assembly
100 according to the present invention.
Layer 62 serves as the channel between source and drain electrodes
64 and 66. The conductance of the conjugated molecular assembly
layer may be modulated across and electrically insulating layer 68,
such as a thin SiO.sub.2 film, by a gate electrode 70, which may be
a degeneratively doped silicon layer, all of which are fabricated
on substrate 72.
FIG. 12 shows a cross-sectional view of a two-terminal vertical
electronic device 1200. The device 1200 includes a conjugated
molecular assembly layer 82 which serves as the active switching
medium between electrodes 84 and 86 fabricated on substrate 88. The
layer 82 (e.g., in combination with electrode 86) includes the
conjugated molecular assembly 100 according to the present
invention. In this case, electrode 84 may be deposited on top of
the conjugated molecular assembly.
FIG. 13 shows a cross-sectional view of a three-terminal vertical
electronic device 1300 in the configuration of a transistor. The
device 1300 includes a conjugated molecular assembly layer 92 which
(e.g., in combination with source 96) includes the conjugated
molecular assembly 100 according to the present invention.
Layer 92 serves as the channel between source and drain electrodes
94 and 96. The conductance of layer 92 (e.g., the conjugated
molecular assembly) is modulated across an electrically insulating
layer 98, such as a thin SiO.sub.2 film, by a gate electrode 100,
which may be a degeneratively doped silicon layer, all of which are
fabricated on substrate 102. In this case, electrode 94 may be
deposited on top of the conjugated molecular assembly.
FIG. 14A illustrates a cross-sectional view of a two-terminal
lateral sensor device 1400 according to the present invention. This
device 1400 includes an active sensing medium layer 114 (between
electrodes 116 and 118) fabricated on substrate 128, which serves
as the active sensing medium between electrodes 116 and 118. The
active layer 114 (e.g., in combination with the substrate 128 or
one or both of the electrodes 116 and 118) includes a conjugated
molecular assembly 100 according to the present invention.
As shown in FIG. 14A, the conjugated molecular assembly 100 in the
device 1400 may include the extended conjugated molecule
represented by chemical formula 21 (described above), which is
functionalized (e.g., with receptors 122 sensitive to an analyte
124) to provide a desired sensitivity.
FIG. 14B shows a cross-sectional view of a three-terminal lateral
electronic device 1450 (in the configuration of a transistor) in
accordance with the present invention. The device 1450 includes a
conjugated molecular assembly layer 132 which (e.g., in combination
with insulator 138 or one of both of the electrodes 134 and 136)
includes the conjugated molecular assembly 100 according to the
present invention.
Layer 132 serves as the channel between source and drain electrodes
136 and 134. As shown in FIG. 14B, the conjugated molecular
assembly 100 in the device 1450 may include the extended conjugated
molecule represented by chemical formula 21 (described above),
which is functionalized (e.g., with receptors 144 sensitive to an
analyte 146) to provide a desired sensitivity The conductance of
the conjugated molecular assembly may be modulated across an
electrically insulating layer 138, such as a thin SiO.sub.2 film,
by a gate electrode 140, which may be a degeneratively doped
silicon layer, all of which are fabricated on substrate 152.
According to the present invention, a conjugated molecular assembly
may be formed by depositing compounds from solution by stepwise
construction. The low-cost, solution-based deposition is compatible
with inexpensive, large area electronic applications. In addition,
the low-temperature deposition conditions are compatible with a
variety of substrate materials, including plastics, for flexible
electronic applications.
Further, the present invention provides a molecular electronic
device having an extended conjugated molecular assembly layer
(e.g., an insulating layer) prepared by stepwise construction. The
insulating layer may be disposed on the substrate or may be
incorporated into the molecule.
With its unique and novel features, the present invention includes
a conjugated molecular assembly (and method of fabricating the
assembly) which includes molecules with long molecular lengths
(e.g., extended conjugated molecules) and allows for a wide range
of functionality. The present invention also provides an improved
molecular device having improved electrical properties or sensor
properties.
While the invention has been described in terms of preferred
embodiments, those skilled in the art will recognize that the
invention can be practiced with modification within the spirit and
scope of the appended claims. Specifically, one of ordinary skill
in the art will understand that the drawings herein are meant to be
illustrative, and the design of the inventive assembly is not
limited to that disclosed herein but may be modified within the
spirit and scope of the present invention.
Further, Applicant's intent is to encompass the equivalents of all
claim elements, and no amendment to any claim the present
application should be construed as a disclaimer of any interest in
or right to an equivalent of any element or feature of the amended
claim.
* * * * *